A pressure measuring instrument, which is called as a diaphragm-type pressure gauge, has been widely known. In the pressure measuring instrument, a diaphragm (e.g., a diaphragm-type sensor) is disposed between a reference pressure chamber and a measurement pressure chamber and the pressure of the measurement pressure chamber is measured based on a deformation amount of the diaphragm, in which the diaphragm is deformed due to a difference in pressure between the reference pressure chamber and the measurement pressure chamber. A deformable elastic body (e.g., a thin film, etc.) is used as the diaphragm of the pressure measuring instrument. In the pressure measuring instrument, if particles, reaction products and the like adhere to the diaphragm, the adhering particles and the like apply stresses to the diaphragm, thereby affecting the deformation amount (deflection amount) of the diaphragm.
In the related art, there is disclosed a technology in which a plurality of T-like projections is formed on a surface of a diaphragm to capture particles and the like existing in a gas.
According to the related art, it is possible to reduce particles and the like adhering to the diaphragm. However, due to the formation of the T-like projections, the surface structure of the diaphragm becomes complex. In the related art, the T-like projections formed on the surface of the diaphragm can capture solids (particles and the like) contained in a gas. However, sometimes, the T-like projections cannot capture deposits (adhering materials) deposited on the surface of the diaphragm.
For example, in order to measure the internal pressure of a process chamber with a pressure measuring instrument in case that a substrate is processed by an atomic layer deposition (ALD) method or a molecular layer deposition (MLD) method, it is necessary to measure the internal pressure of the process chamber when two kinds of gases reacting with each other are alternately supplied. In this case, two kinds of gases reacting with each other alternately make contact with a surface of a diaphragm, reaction products (deposits) of two kinds of gases may be generated (deposited) on the surface of the diaphragm. In other words, according to the related art, there is a case that the deposits on the surface of the diaphragm cannot be captured by T-like projections formed on the surface of the diaphragm. Moreover, in the related art, there may be a case that the stresses generated by deposits make it impossible to accurately measure the deformation of the diaphragm attributable to the difference in pressure between the reference pressure chamber and the measurement pressure chamber.